The following descriptions relate to a connection mechanism for connecting a plate member and a shaft member employed, for example, in an endoscope.
Generally, at an operation section of an endoscope, connection mechanisms such as a mechanism for operating a bending portion of an insertion section of the endoscope, a mechanism for changing an rising angle of a treatment tool and the like are provided. Such a mechanism employs a connection mechanism which connects the plate member with the shaft member such that the plate member does not rotate relative to the shaft member.
Typically, in such a connection mechanism, a portion of the shaft member is formed to have a shape of a polygonal column, and a polygonal opening to be engaged with the polygonal column portion is formed on the plate member. By fitting the polygonal column portion into the polygonal opening, the plate member and the shaft member do not rotate with respect to each other. An example of such a configuration is disclosed in Japanese Patent Provisional Publication No. HEI 9-98942.
When the above structure is employed, due to manufacturing errors, there may be some play between the plate member and the shaft member in the rotational direction. If an endoscope having such a problem is shipped as a product, an operator of the endoscope may not operate the endoscope (e.g., the operator may not control the degree of bend of the bendable section as intended).
FIG. 9 shows a conventional connection mechanism to deal with the above problem, and FIG. 10 is a cross section taken along line X-X in FIG. 9. In FIGS. 9 and 10, 92 denotes the plate member, and 91 denotes the shaft member. According to this example, screw holes 93 which extend substantially in a radial direction with respect to a central axis 91ax of the shaft member 91 are formed on the plate member 92. The shaft member has a polygonal column section 91x which is inserted in a polygonal opening 92x. Then, by inserting screws 94 through the screw holes 93 and fastening the same, tip ends of the screws 94 press-contact the polygonal column section 91x in the radial directions, respectively, thereby play between the plate member 92 and shaft member 91 can be prevented.
In order to prevent the play between the plate member 92 and the shaft member 91 effectively, however, as shown in FIG. 10, at least three screws 94 should be used to push the polygonal column section 91x in different directions. That is, if only a single screw 94 is used, the plate member may incline with respect to a plane perpendicular to the central axis 91ax of the shaft member 91. Since the three screws 94 should be employed, assembling work of the structure shown FIGS. 9 and 10 is inefficient. Further, in the structure shown in FIGS. 9 and 10, the screws 94 may be loosened relatively easily, and after elapse of a relatively short period, play may occur between the plate member 92 and shaft member 91.